Well I'd recommend the XP30. It belongs to the JV/XP family which happens to include the most expandable synths in the world.

The JX305 lokks great but cannot be upgraded the same way.

PC sequencing using Cakewalk or Cubase is definately easier than hardware sequencing however it's useful to have an onboard sequencer for traveling purposes and you can always transfer the pc data to the XP sequencer . Another viable option is a cheap laptop 486 pc. Nothing fancy.

Music is changing rapidly. It's gone through tons of various stages of Dance in the last decade and you'll find that groove programming will fall out of favour with the masses for a while.

Get yourself a wholesome instrument suited to more musical applications without comprimising on the one you prefer. The XP30 or the XP60/80 with onboard sequencers.

The Music is the all important thing here. Not the kit you use to make it.

Have Fun.